The present invention relates generally to variable pitch radiator fans, and in particular to a fan blade pitch change assembly for a variable pitch radiator fan.
Variable pitch radiator fans for use in motor vehicles have been proposed. U.S. Pat. No. 6,896,564 teaches a propeller for a boat including a phase adjuster for altering the pitch of the propeller blades. In the '564 patent, an internal combustion engine turns a drive shaft coupled to a propeller shaft. A second shaft is positioned inside of and coaxial with propeller shaft. The second shaft is linked to the propeller blades by a bevel gear. The two shafts are coupled by a planetary gearing system. An actuator shaft is rotated by a servo motor and is coupled to the planetary gear of the second shaft by a worm gear via a moveable orbit gear. When the propeller shaft is rotated by the drive shaft, the second shaft turns in phase with the propeller shaft due to the planetary gearing system. However, if the servo motor is actuated, the actuator shaft rotates to drive the worm gear and moves the orbit gear. The movement of the orbit gear shifts the planetary gear on the second shaft so that the second shaft moves out of phase with the propeller shaft. This differential drives the bevel gear and moves the blades to change their pitch.
U.S. Pat. No. 5,281,094 teaches a variable pitch fan blade mechanism. An internal combustion engine rotates a fan shaft. The fan shaft is connected to a fan hub so that the fan hub rotates with the fan shaft. Fan blades are attached to the fan hub via a gearbox. The gearbox is also attached to a control shaft that is coupled to the fan shaft via the gearbox. An induction motor and an induction brake are mounted so that the squirrel cage rotors are mounted on the control shaft and the stators are mounted on a stationary frame housing the fan unit. To change the blade pitch in one direction, the induction motor is actuated to cause the control shaft to rotate at a different speed than the fan shaft. This differential in rotational speed drives the gearbox to shift the position of the fan blades. To change the blade pitch in the opposite direction, the induction brake is actuated to rotate the control shaft at a different speed than the fan shaft to move the fan blades in the opposite direction.
U.S. Pat. No. 3,967,916 teaches a fan assembly with a plurality of variable pitch blades. A main fan shaft is driven by a motor to turn a blade assembly. The blade assembly includes a plurality of fan blades that are rotatably attached to a frame structure. A pneumatically-driven pitch control rod is positioned coaxially within the main fan shaft and extends out of the main fan shaft inside the frame structure. The pitch control rod includes a series of notches which engage a gear connected to the fan blades. When actuated, the rod moves axially within the main fan shaft to drive the gear to alter the pitch of the fan blades.
While the art teaches various blade pitch mechanisms, the related art fails to teach a blade pitch mechanism that includes two independently operating drivers for controlling the variation in the pitch of the fan blades. Therefore, a need exists in the art for a variable blade pitch mechanism having dual shaft and dual driver control.